If you choose zero targets, you’ll just scry 1 when the ability resolves. However, if you choose at least one target and all of Sudden Storm’s targets are illegal as it tries to resolve, the spell won’t resolve and none of its effects will happen. You won’t scry in that case.
Sudden Storm
If a creature affected by Sudden Storm changes controllers before its old controller’s next untap step, Sudden Storm will prevent it from becoming untapped during its new controller’s next untap step.
If you chose two targets and one is an illegal target when Sudden Storm resolves, that creature won’t become tapped and it won’t be stopped from untapping during its controller’s next untap step. It won’t be affected by Sudden Storm in any way.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Adam Paquette
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
